obama recalled it was mandela's work-- worlds away-- that helped fuel his own desire to enter public service. >> over 30 years ago, while still a student, i learned of nelson mandela and the struggles taking place in this beautiful land, and it stirred something in me. it woke me up to my responsibilities to others and to myself, and it set me on an improbable journey that finds me here today. and while i will always fall short of madiba's example, he makes me want to be a better man. >> ifill: under tight security, the president and nearly 100 other heads of state and government filed into the stadium. they included three former u.s. presidents: jimmy carter, bill clinton and george w. bush. brazil's president dilma rousseff pointed to mandela's long battle against apartheid and the example he set for many in the developing world. >> ( translated ): mandela's fight and that of the south african people as a whole became a paradigm, a model not only for this continent but also for those who fight for justice, freedom and equality. >> ifill: and cuban president raul castro paid special